Hello all, new to the forum and new to old cars and trucks. I just bought a 1974 GMC Suburban 3/4 ton with an Olds 455 in it. I'm am trying to figure out what the engine came from so I can get parts.

My first question is where do I find what numbers on the engine? Once I find them hopefully you can tell me what they mean.

At quick glance there's some individual letters on the heads and there's a 6-9 digit one on the shelf between the water pump and front of the intake manifold.

 

The numbers on the water pump shelf will tell you what block it is - 396021F or 396021Fa is a 455 block.
The heads are identified by a letter on the corner by the #1 spark plug.
There is a VIN pad on the block by the #1 cylinder that will tell the year of manufacture, the assembly plant, and the partial VIN of the vehicle it was put in.

 

Thank you I'll go take pictures. The year is important to order some parts though so it's better than nothing right?

 

Not really. First, except for piston dish size (which determines compression ratio), all internal parts from 1968-1976 interchange. The only part that depends on the year is the intake gasket, due to the size of the heat crossover ports, and this depends on the year of the HEADS, not the block. Second since this engine is not original to the truck anyway, you have no idea as to what was done to it previously. Third, as with pistons, cam varies by year and application, but all interchange across all years of 455 production. Bottom line, the year of the motor pretty much won't change what parts you order.

 

What about if it was car vs Marine?

 

Well, if it is in a car the the marine exhaust manifolds and other parts have been replaced with regular car parts, so again, it's just a 455 engine.

 

Ok I wasn't sure if there was any significant difference. The only thing I need to know now is if it has a pilot bearing spot in the crank so I can yank this broken 700R4 for an SM465

 

Unlikely that you can figure that out without pulling the transmission and looking. As far as I know Olds only machined the crank for a pilot bearing if it was destined for a car with a manual transmission.